6 months ago, I would have highlighted NRR (renewal + expansion) and Adoption. However, after having learned what companies like Plex and Workday are doing to capture customer outcomes during the sales process and then as vendors map their product/service features and/or usage to proactively measure and even quantify realized business impact against customers' desired outcomes. So, now I would expect to see a customer KPI around business impact.
This is an emerging area as the TSIA reports that less than 20% of technology vendors are currently capturing customer outcomes during the sales process.
With expansion metrics like net dollar renewal rate (DRR), net dollar retention (NDR), expansion metrics like net expansion rate (NER) and customer health metrics like consumption (low adoption) it can all be a bit much.
I have seen companies only looking for license growth. Others want to see other kinds of revenue or it could be both. My answer would be that the Executive of Customer Success should have KPIs his boss wants him to be successful in - and this is exactly what you need to use. And this may not be the same each year and for sure not the same in each company.
This is a great question. And I think an area that is still being standardized in the industry. If you'd like to see more on this, there's a recent blog post that has been popular.